Vector-borne Viruses Flashcards
What are arboviruses
viruses that are transmitted by an insect
How can insects acquire an arbovirus
through a blood meal of a reservoir or infected individual OR
vertical transmission between mother mosquito and offspring
What are characteristics of arbovirus infections
viruses must establish a viremic (blood) infection
have access to virtually all organs increase the potential for severe disease
often have an insect and reservoir host and most of the time they do not cause disease in the insect or reservoir host
if the virus gets into a non-reservoir host it can cause severe disease
The majority of viruses that use mosquitos as vectors belong to the ___ family(ies)
Flavivirus and Togavirus
one has the Bunyavirus
What virus causes Yellow fever virus
Flavirus which is a simple + ssRNA virus
What does the yellow fever virus cause
causes a hemorrhagic fever, symptoms include headache, backache, muscle aches, fever, and chills
Where does yellow fever virus get its name
gets its name from the jaundice that is occasionally associated with the disease
Where is yellow fever geographical distributed
virus is primary in South America and Africa
200,000 cases
30,000 deaths per year
What mosquito spreads the yellow fever virus
Aedes aegypti mosquito
Explain the yellow fever virus transmission cycle
main reservoir host is a monkey which is maintained in the sylvatic cycle (jungle cycle) and the viral infection does not cause disease in monkeys
occasionally a human will enter the jungle and become infected with the yellow fever virus
and this person can transmit the virus to another mosquito which can got into an urban area
an urban cycle can happen after this, this is when the virus spreads from the blood of a humans into the mosquito and then to other humans, may be a different mosquito than the sylvatic cycle mosquito
What is the main reservoir of the yellow fever virus
monkey and is maintained in the sylvatic cycle
What is the sylvatic cycle
the jungle cycle
mosquito to monkey and so on
What was the first human virus discovered
yellow fever virus
What is viremia
virus is in the blood and can easily spread to major organs
What is the historical aspects of the yellow fever virus
brought to the Americas during the years of the slave trade, also brought the mosquitos
has played an important role in the human history especially in the wars in South America and the Caribbean
Napoleon in 1801 sent 40,000 troops to Haiti only 3000 returned most of the remaining ones died of yellow fever
Mexican-American war of 1846-47 10X more soldiers were killed by yellow fever than by battle
1901 Walter Reed confirmed the route of infection and nature of the agent of disease
What are the detailed aspects of yellow fever disease
- virus elicits an innate immune response that leads to production of pro-inflammatory cytokines at the site of infection
- cytokines recruit immune cells to the site of infection, the virus gets into the immune cells
- infected immune cells traffic to the lymph nodes
- virus amplifies in the lymph nodes and enters the circulatory system (viremia)
- they then travel to the liver, the liver is the primary target
- large number of hepatocytes die from the virus infection or apoptosis
- cytokine storm which causes damage to many cells throughout the body that leaves to hemorrhage (leaking of blood)
How is yellow fever prevented or treated
vaccine that affords lifelong protection
yellow fever still afflicts several hundred thousand individuals each year
other methods to prevent mosquito bits have limited affects (bed nets)
Is it possible to eliminate yellow fever
nearly impossible to eliminate due to the inset and vertebrate reservoirs
can limit infection by vaccines
What virus causes the the Dengue Virus
Flavivirus which is +ssRNA
Where geographically is the dengue virus
mainly in Asia and Latin America
endemic in southeast Asia, Africa, Caribbean and the Americas
How many cases of dengue virus is there
estimate 400 million cases each year
500,000 get severe disease and 2.5% of cases result in fatality
40% of worlds population at risk
How is dengue virus transmitted
between humans by Aedes aegypti and also Aedes albopictus
in 1960s it was only known to occur in a few countries since then it has spread to more than 100 countries
40% of worlds population is at risk
What are aspects of the dengue virus cases
complex disease
95% of cases result in asymptomatic or mild disease
even in the mild cases the virus often caused headaches and muscle/ joint pains that eventually gave the virus the name break bone fever
in 5% of cases the dengue fever progresses to a more severe, life-threatening fever/ shock syndrome
What are aspects of the dengue virus disease
complex disease
hemorrhagic fever associated with GI bleeding and plasma leakage
can lead to hepatic failure which generates the shock syndrome
virus illicits a very strong innate immune response called a cytokine storm
brings immune cells to the sites of vascular damage and thus causing further damage
What is ADE
antibody dependent enchantment
What virus causes antibody dependent enhancement
dengue virus
How does dengue virus cause an antibody dependent enchancment
dengue virus exists as multiple serotypes, serotypes are groups of organisms with the same antigen
5 differs serotypes DENV-1, DENV-2 and so on
epitopes are slightly different between the different serotypes
antibodies can bind and neutralize DENV-1 , but if someone was infected with DENV-2 the antibody would bind to DENV-2 but would not neutralize t, this also the dengue virus to infer macrophages
the macrophages have bonded to the Fc region of the antibody and take up the virus, the virus wants to be inside of the macrophage to travel through the body, the virus can kill the macrophage after replication
rapid amplification of virus production occurs and this is called ADE
Why is the dengue virus so hard to make a vaccine for
because it has 5 differs serotypes and this causes antibody dependent enhancement (ADE)
What is the primary target of he dengue virus
macrophages
What are possible treatment or prevention methods for he dengue virus
no vaccine
no therapeutics
only preventive measures are on reducing opportunities for the insects to persist in urban areas
supportive treatment (maintaining fluids and blood) can reduce mortality of severe cases from 10% down to 1%
What virus causes the Chikungunya virus
alphavirus which is a +ssRNA
Where was the Chikungunya virus first discovered
first discovered in 1952 in Tanzania (eastern edge of Africa)
Where was the big outbreak of the Chikungunya virus and why did this likely occur
2005-2007 there was a large outbreak on reunion island (off the eastern coast of Madagascar)
1/3 of the population because infected
this resulted in rapid widespread distribution of southern Africa and Southeast Asia
this rapid spread was because of the change in mosquito vector, the mosquito that it enters into had a larger geographical range
What are aspects of Chikungunya virus transmission
primary reservoir is not clear
several animal species including bats, birds, and primates can ac as reservoirs
originally transmitted by Aedes aegypit and its vector changed to Aedes albopictus since the outbreak on region island
the increase spread is because Aedes albopictus has an extend geographical range
What are the disease symptoms of the chikungunya virus
disease is the result of extensive viremia
virus targets cells in he vicinity of the mosquito bite
virus is transmitted to secondary lymph glands
induces a cytokine storm
virus is carried into synovial tissue of joints by infected monocytes and macrophages where the inflammatory response is established
What are the symptoms of the Chikungunya virus
symptoms occur in 4-30% of those infected
initial disease is self-limiting
it can include high fever, nausea, headache, rash, petechial spots and joint pain, low mortality rate of about .1%
joint pain is a major problem and it does not go away
joint pain appears in several episodes many months or years after initial infection
How is CHIKV prevented or treated
no vaccine or therapeutic drugs
effort focused on controlling mosquito vector and addressing symptoms of the disease
anti-inflammatory drugs to reduce pains associated with severe arthritis caused by the virus
Does CHIKV have a vaccine
no
Does dengue have a vaccine
no
Does Yellow fever have a vaccine
yes
